12-7A-4.8 Part B. Burning Brand Exposure
- Wind tunnel. The wind tunnel shall have the capability of providing 12 mph (5.4 m/s) airflow over the deck assembly.
- Anemometer. Device for measuring airflow across the deck.
- Burner. Gas-fueled burner for brand ignition.
See Figure 2. The ASTM E 108 "A" brand roof test apparatus is to be used, with the following modifications:
- Deck support. The deck shall be supported horizontally with the center 60 inches (150 mm) from the front opening of the wind tunnel and the joists parallel to the airflow and resting on two transverse metal supports. The top surfaces of these supports, no more than 3 inches (75 mm) wide, are at the same height as the floor of the wind tunnel.
- Fragments. Burning fragments shall be free to fall to the floor of the room.
- Number of tests. Conduct the test on three replicate assemblies.
- Moisture content. Measure the moisture content of the wooden members of the assembly using a moisture meter (ASTM D 4444).
- 3.1. The air velocity shall be calibrated using the 60-inch (1.5 m) framework spacing, with a smooth noncombustible calibration deck at a 5-inch per 12-inch horizontal incline positioned 60 inches (1.5 m) from the front opening of the wind tunnel. All other measurement details shall be followed as specified in Sections 4.4.2, 4.4.3, and 4.4.4 of ASTM E 108. Although ASTM E 108 specifies calibration to be conducted with the 33-inch (840-mm) framework spacing used for the intermittent flame test set up, tests have shown that at the nominal 12 mph setting, there was not difference in measured velocity between the 33- and 60-inch framework spacing.
- 3.2. Mount the test specimen at a zero horizontal incline positioned 60 inches (1.5 m) from the front opening of the wind tunnel.
- Each 12- × 12-inch (300 × 300 mm) face for 30 seconds.
- Each 2.25- × 12-inch (57 × 300 mm) edge for 45 seconds.
- Each 12- × 12-inch (300 × 300 mm) face again for 30 seconds.
- 3.4. Center the burning brand laterally on the deck with the front edge 2.5 inches (64 mm) from the entering air edge of the deck.
- Observations. Note physical changes of the deck boards during the test, including deformation from the horizontal plane, location of flaming and glowing combustion, and loss of material (i.e., flaming drops of particles falling from the deck). It is desirable to capture the entire test with a video recorder to allow review of the details of performance.
Should one of the three replicates fail to meet the Conditions of Acceptance, three additional tests may be run. All of the additional tests must meet the Conditions of Acceptance:
- Absence of sustained flaming or glowing combustion of any kind at the conclusion of the 40-minute observation period.
- Absence of falling particles that are still burning when reaching the burner or floor.